Bonding or welding of two or more polymeric components can be accomplished according to a variety of methods. For example, in the construction of medical devices, such as balloon catheters, or the like, it is known to bring the polymeric components of the catheter into contact with a medium which is at the melting temperature of the polymers. More specifically, the polymeric components can be placed within a heated clam shell, or mold-type of device, which surrounds the polymeric material, and transfers heat from the material of the clam shell to the material of the polymeric component. Alternatively, the polymeric materials can be exposed to a hot air stream which is at a temperature sufficient to melt the polymer. A disadvantage of such systems is the time required to bring the polymer to a molding temperature is so great that the transferred heat tends to dissipate throughout the polymeric material and to any adjoining areas of the device. It is therefore difficult to restrict the area affected by the heat.
According to other techniques, it is known to expose a form of energy to the welding area to heat the polymeric material either by direct absorption by the polymeric material, or indirectly, by adding an energy-absorbing additive through the polymer. For example, with regard to laser welding, it is known to disperse an additive throughout the polymeric material which is adapted to absorb the laser frequency. The polymeric material is heated by the hysterisis losses resulting from the laser frequency absorbing additive. While the polymeric material can be heated quickly according to such a method, and the welding spot can be precisely located by direct placement of the energy-absorbing additive, it is difficult to control the temperature accurately.
In still further systems, it is known to add ferromagnetic materials to the polymeric materials and then expose the combined materials to an electromagnetic field. The polymeric material is thereby heated due to hysterisis losses associated with the vibrating ferromagnetic materials. Moreover, one advantage of such a system over the above-referenced laser welding system is that temperatures can be more accurately controlled due to the fact that the hysterisis losses will only occur up to the Curie temperature of the ferromagnetic material. By selecting a ferromagnetic material with a Curie temperature equal to a point at which the polymeric materials will bond, it is possible to heat and bond the polymeric materials, without damage to the polymeric materials due to overheating of the material. Moreover, the materials can be heated quickly with such a system.
Additionally, the electromagnetic field can pass through all polymers and therefore heat ferromagnetic material placed on the inside of such structures, therefore enabling heating from the inside out.
While such systems are effective, the addition of the ferromagnetic material to the device being created has certain inherent drawbacks. For example, the particle size of the ferromagnetic materials currently in use, which are on the order of at least one micron, is such that the particles themselves are often as thick as the walls or individual polymer layers of the devices being created, thereby creating weak spots due to a lack of a chemical connection between the polymer matrix and the ferromagnetic particles. The addition of the ferromagnetic material will also often stiffen the bond site, a disadvantage when the medical device being created must be flexible. A disadvantage of large (i.e., larger than one micron) ferromagnetic particles is the relatively small surface-to-volume ratio in comparison to smaller nano-sized ferromagnetic particles.
In some bonding systems, dissimilar polymeric materials, each containing a micro-dispersion of fine-micron ferromagnetic powders may be bonded to one another using a specially compounded thermoplastic elastomer, containing ferromagnetic material. The compound material contains material similar to that in the polymeric materials being bonded, and the entire composite is heated to the fusion temperature of the same polymeric materials in order to form a chemical bond. The heat is generated using a high alternating current source that results in heat losses between the thermoplastic base material and the abutting joint surface with the heat flowing from the metal filler and melting the adjoining surfaces. However, this technology is in need of further refinements. Such bonding systems have been used in the consumer appliance, automotive and large medical device markets. However, such systems have not been employed in the context of catheter assembly, an area which introduces unique constraints and difficulties. Catheter assembly is characterized by tight (narrow) tolerance, small bond gap applications, and one would not expect success using existing bonding techniques. Additionally, it would be advantageous to have a bonding process for catheter assembly and other contexts that would permit binding of polymeric materials that themselves do not necessarily contain ferromagnetic materials.
At present, catheter bonding technologies are typically limited to two primary technologies: adhesive bonded catheters and thermally bonded catheters. Adhesive-bonded catheters include catheters that require high melt flow polymer adhesives to join incompatible polymeric components together. This technology is undesirable from an operational cost and efficiency perspective due to relatively lengthy cure times, etc. Thermally-bonded catheters include catheters that join compatible polymeric components together. This technology is substantially limiting because the polymeric components to be joined must be of substantially similar, if not identical composition.
Accordingly, there exists a need for more efficient, cost-effective means for bonding catheter components, polymeric materials in general and especially dissimilar materials together.